Re: Fugitive pigments

From: Katharine Thayer ^lt;[email protected]>
Date: 07/25/05-03:01:01 PM Z
Message-id: <42E5530A.497B@pacifier.com>

Katharine Thayer wrote:
>
> David & Jan Harris wrote:
> >

> It would be interesting to know which wavelength of light is most
> > active in causing the gum/dichromate hardening reaction - one for the
> > chemists to think about! Do we all use UV just because it's the easiest way
> > to get a suitable light intensity, or is the UV itself necessary?
>
> UV itself -- my understanding from my reading is that there are peaks at
> 365 and 440 nm (although 440 is in the visible range) but I think it
> depends on the colloid as well; those numbers are probably for PVA.
>

P.S. I think Joe's right, it's the dichromate whose absorption spectrum
is relevant here, so you wouldn't think it should be different for
different colloids. I would have to go back through my research papers
to find out what that 365 and 440 refers to, that I've read in the
research on dichromated processes.
kt
Received on Mon Jul 25 21:56:40 2005

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